"deliberately disabling the transponder"
It probably was deliberate but not intentionally deliberate. I had an emergency a few years back, which actually turned out to be two mutually exclusive events that came together at the same time which caused us "the entire crew" that we had a fuel leak. Without getting into the event, my first officer not only selected standby on the transponder prior to setting 7700 he didn't switch it back on either. I only noticed because the TCAS was off. A case of unintentional but deliberately disabled. How many of us in the heat of the moment would forget you dont need to select standby when changing codes.